The present invention is directed to a sample container and preferably, to a sample container containing a liquid microorganism growth media, wherein the sample container has good long term stability. More particularly, the present invention is directed to a microbial detecting container that is optically transparent, heat resistant, and resistant to breakage.
A vast number of microorganisms are known, many of which are harmful to humans. The presence of these microorganisms creates a continuing need for reliable detection systems and methods of safely and efficiently handling microorganism samples.
In recent years there has been an increased incidence of mycobacterial diseases, and particularly, tuberculosis. To address this increase of such diseases in the population, numerous methods have been introduced for improving the detection of the presence of various mycobacteria, such as, tuberculosis. A number of methods are directed to reducing the time required for accurate detection of the microorganism.
One type of detection system relies on the visual detection of the presence or absence of the growth of microorganisms. Antimicrobic susceptibility tests use this kind of visual detection as an indication of the efficacy of an antimicrobic compound. A disadvantage of this type of test is the time requirements which can require an 18 to 24 day incubation period before sufficient microorganism growth can be detected. An example of this type of method is the Bauer-Kirby Disc Method.
Another method of testing antimicrobic susceptibility uses a plastic panel having several low volume cupulas. Each cupula contains a different test compound or different concentration of a test compound dried on the cupula surface. A test sample containing the suspected microorganism is suspended in a testing medium and an aliquot is delivered to the individual cupulas of the test panel. The dried reagent dissolves and the resulting solution is incubated for sufficient time for the organisms to interact with the reagent and grow. The samples are visually examined for the presence or absence of growth. This method also has the disadvantage of long incubation times thereby preventing a rapid detection.
Light scattering methods have also been developed for determining the susceptibility of microorganisms to antimicrobic compounds. These methods require the use of a light scattering and detection apparatus that are able to detect and measure the changes in size of the microorganism colonies or changes in the number of the microorganism colonies. Information on the antimicrobic susceptibility of various microorganisms have been reported in as little as six hours. However, some microorganisms and antimicrobic compounds can require as long as 18 hours to obtain reliable results.
Another method of determining antimicrobic susceptibility is based on quantifying ATP in the microorganism during incubation by a bioluminescent method. Although this method can produce results in less time than other methods, the method can be difficult to carry out properly to obtain accurate results.
The growth of microorganisms has also been detected by measuring changes in dissolved oxygen. Measuring dissolved oxygen often uses a suitable electrode. However, some of the electrode systems consume oxygen thereby increasing the difficulty of obtaining accurate measurements. Some electrodes require an oxygen permeable membrane to prevent the electrode from interacting with the growth media and the microorganisms. This system still consumes some oxygen and requires time for the solution to equilibrate with the electrodes.
Various methods for optical detection of changes in oxygen concentration have been developed that do not require the use of electrodes in the test solution. These devices can be based on calorimetric or fluorimetic analysis based on changes in the oxygen content of the solutions. These optical processes can be performed economically and in a reasonable time period. One example of a process for detecting microorganisms by detecting changes in oxygen levels is disclosed in U.S. Pat. No. 5,567,598 to Stitt et al. The process disclosed in this patent detects and evaluates the metabolic activity of microorganisms using a fluorescent compound.
Many of these methods require the use of a container or sample tube to contain the sample during the analysis. Glass is a common material for the sample tubes since glass is typically non-reactive with the samples or the instrumentation. A disadvantage of glass tubes is the risk of contamination or exposure to pathogens in the event of breakage. Most non-breakable tubes are not suitable for autoclaving and for use in optical detection systems since the container material interferes with the detection system. Accordingly, there is a continuing need in the industry for improved sample tubes.
The present invention is directed to a sample container suitable for use in an optical detection system. More particularly, the invention is directed to a sample container made from a cyclic olefin copolymer. The invention is further directed to a method of detecting organisms using the sample container.
Accordingly, a primary object of the invention is to provide a sample container for detecting the presence of microorganisms by fluorescence analysis.
Another object of the invention is to provide a non-breakable sample container produced from a cyclic olefin copolymer that is optically clear to allow visual detection of a fluorescent compound by ultraviolet light and visual inspection of a microorganism growth medium.
A further object of the invention is to provide a sample container made from a cyclic olefin copolymer that is heat resistant to at least 250xc2x0 C. without distortion or hazing of the container.
A still further object of the invention is to provide a sample container made from a cyclic olefin copolymer that is able to withstand an internal pressure of about 25 psi without rupturing or distortion.
Another object of the invention is to provide a sample container made from a cyclic olefin copolymer that is non-reactive with a liquid microorganism growth media and provides a shelf stable environment for a microorganism growth media for extended periods of time.
These and other objects of the invention are basically attained by providing a sample container assembly comprising a container having a side wall, a bottom wall, an open top end, and a liquid sample contained therein, the container being formed from a cyclic olefin copolymer having a transparency sufficient to visually observe turbitity in said sample; and a closure coupled to the open end of the container, wherein the sample is substantially free of contamination upon prolonged storage of preferably about one year at 40xc2x0 C.
The objects of the invention are further attained by providing a microbial detecting container assembly comprising a transparent container having a side wall, a bottom wall and an open top end, a fluorescent sensor compound that exhibits a reduction in fluorescent intensity when exposed to oxygen, and a microorganism growth media contained within the container, the container being made by a molding process from a cyclic olefin copolymer, wherein the container has a transparency sufficient to visually detect turbidity in the microorganism growth media, and wherein the microorganism growth medium is substantially free of contamination after storage for, preferably, at least about 1 year at about 40xc2x0 C.; and a closure coupled to the open end of the container.
The objects of the invention are also attained by providing a method of detecting the presence of microorganisms in a sample comprising providing a transparent container having a sidewall, a bottom wall, an open top end, and a closure coupled to the open top end, the container containing a microorganism growth medium, wherein the container is made by a molding process from a cyclic olefin copolymer, the container having a transparency sufficient to visually detect turbitity in said bacterial growth media and said bacterial growth medium being substantially free of contamination after storage for, preferably, at least about 1 year at 40xc2x0 C., adding a sample to said transparent container, irradiating said fluorescent sensor with a light source capable of fluorescing said fluorescent sensor, detecting fluorescent light intensity from said fluorescent sensor while irradiating said fluorescent sensor, and comparing said detected fluorescent light intensity with a control and determining the presence of microorganisms in the sample.
The objects advantages and other salient features of the invention will become apparent from the following detailed description of the invention which taken in conjunction with the annexed drawings disclose various embodiments of the invention.